AutoSleep is my go to sleep tracking app for the Apple Watch and it got a big update today:

Much faster, simpler and more accurate.

Now with automatic “live” sleep tracking on the Watch face! No buttons to press.

iPhone X Support. Optimised for WatchOS 4.

I love this tracker because it requires literally zero input from me. After giving the app access to your movement data, it will automatically keep track of your sleep every night. It’s the only sleep tracking app I’ve ever used that doesn’t require any user input, which is huge!